1. Field of the Invention
This invention pertains generally to devices for cleaning and liquid contact with solids having alarm, signal, indicating, testing, inspecting, illuminating or display means to be found in U.S. Patent Office Class 134, subclass 113. The invention particularly relates to an apparatus easily adapted to preexisting commercial dishwashing machines for indicating visually and/or audibly the absence of an additive within the supply line leading from the separate additive reservoir to the point within the dishwashing machine where the additive is normally added. The additives contemplated include all liquid alkaline and bleaching additives as well as low-foaming wetting agents and other commercial surfactants having general utility in the prewash, washing, or rinsing cycles of commercial dishwashing machines.
2. Description of the Prior Art
Conventional commercial dishwashing machines now known to the trade and used in restaurants, hotels, hospitals, and other such institutions typically include a wash water tank or sump which contains a quantity of water and detergent in solution for cleansing the dishes and cutlery placed within the apparatus. Such dishwashing machines normally include means for moving trays of racks of dishes and cutlery through an enclosed housing where they are exposed to jets or sprays of liquids of predetermined temperature and chemical makeup so as to achieve maximum cleansing efficiency with minimum time and waste of natural resources. The addition of additives such as detergents, water softeners, water tension control agents and the like is typically controlled by a central control means controlling individual pumps connected by way of supply lines to reservoirs containing the particular additive intended for a particular purpose. Examples of dishwashing machines of this type are to be found in U.S. Pat. Nos. 3,139,890, 3,319,637, 3,680,784, 3,844,299, and 3,903,909.
The additives contained within the additive reservoirs are usually in concentrated form and must be appropriately diluted with water for the most economical use. In most circumstances a predetermined quantity of an additive is injected by an appropriate pumping means into a line or tank within the dishwashing apparatus. In certain circumstances the addition of the additive is controlled by electrodes which are adapted to sense the concentration of the particular additive in the tank or line in question. In either circumstance, if the content of the reservoir containing the particular additive has been depleted or if the supply line supplying the additive has ruptured there has heretofore been no practical way for indicating this condition to the machine operator.
It has been suggested that the simplest means for monitoring the presence or absence of an additive within the reservoir is to form the reservoirs of a transparent material which is easily visibly checked periodically by the machine operator. In larger installations, however, the reservoirs take the form of standard 15, 30 or 55 gallon steel drums. This renders the visible inspection to determine the level of the contents extremely difficult if not impossible. In such circumstances the prior art has suggested placing wands within each reservoir, each wand containing an electric switch at the lower end thereof sensitive to the presence or absence of the additive by the weight or pressure of the liquid surrounding the switch at the end of the wand. The switch is then appropriately associated with a signal means and a convenient source of power for operating the signal means. While such an indicating means would signal the presence or absence of the additive within the additive reservoir, it would not assure that the additive was actually being delivered by the particular pumping means associated with that additive. Further, it required the careful and delicate repositioning of the wand within the reservoir each time the reservoir was changed when the prior existing contents was depleted. Finally, it was felt that this represented an unnecessarily complicated solution to the problem presented.
Thus, a practical solution was sought to this problem which would immediately indicate the absence of an additive within the delivery line normally delivering that additive to the dishwashing machine and which was consistent with the reliability of commercial equipment performance and inexpensive to install. It was desired that the indicating means could be applied to existing commercial equipment and thereafter require no further handling for its proper operation thus resulting in greatly improved efficiency and reliability. It was also desired that the indicating means would not actually contact the additive in question thus reducing significantly any corrosion problems inherent with the sensing of the presence or absence of the liquids in question. Each of these features and advantages are to be found in the indicating means according to this invention.